A. Case study
A. Case study
A 2-year-old boy was referred because of lactose intolerance. Even though the patient was referred with a specific diagnosis, the same detailed clinical history as is done at any first consultation was taken. This included anthropometry, a medical history and a dietary history, including recent dietary changes and ensuring dietary adequacy. The patient's mother was also questioned about her son's bowel patterns (including recent changes, consistency and frequency), as well as all the symptoms experienced. The patient presented with chronic diarrhoea and flatulence.
Because lactose intolerance fitted into the picture, a lactose-free diet was introduced, as requested by the doctor. But the diarrhoea did not subside. On the follow-up visit, it was established that the diet was followed strictly at home as well as at the playschool, which the patient had started attending the previous week. It was noted that the symptoms were now more severe over weekends than during the week.
Could this be a food allergy? No immediate reactions to food were experienced, so it was unlikely, but delayed reactions to food should always be considered as a possibility. Tests for allergy were done, but were negative. (This topic will be discussed further in a future newsletter.) The presence of flatulence in addition to diarrhoea indicated that intolerance was a more likely cause.
The mother was asked to complete a food-and-symptom diary while her son still followed the lactose-free diet. At the next visit the diary was scrutinised, and there appeared to be a difference between the amount of fruit juice (mostly apple juice) intake at the playschool and at home. The mother saw fruit juice as a healthy and convenient beverage to offer her son whenever he asked for something to drink. Because apple juice is sweet-tasting, her son liked it. A win-win situation?
What do we know about allergies and fruit juice? Most commercially available fruit juices are manufactured with aseptic heat packaging, a process through which most allergens will be denaturated, except for lipid transfer protein, which occur in apples and other fruit. Thus, an allergy is unlikely. What about intolerance? Apple juice has one of the highest fructose contents among fruit juices and can cause gastro-intestinal (GI) symptoms such as flatulence and diarrhoea, especially in young children, due to malabsorption of fructose. Malabsorption has been found in children with intakes of as little as 15ml fruit juice/kg body weight. So, a case of fructose intolerance?
When fructose was excluded from the diet and lactose reintroduced, the diarrhoea disappeared immediately. Fructose intolerance was diagnosed, and it was then left up to the mother to determine what level of fructose (in diluted form) her son could tolerate.
B. Diagnostic testing
Pathophysiologic causes of acute diarrhoea (e.g., Giardia lamblia infection, antibiotic use) are different from those of chronic diarrhoea (e.g., lactose or fructose intolerance).3 Before embarking on expensive and time-consuming evaluations, a thorough diet history and brief restriction of fruit juice intake may be warranted.4
If tolerated, juices with equivalent
fructose-glucose concentrations and low sorbitol concentrations
or no sorbitol may be a good substitute for juices containing
sorbitol and high concentrations of fructose along with low concentrations
of glucose (see below).7 Juices,
because of the relatively high sugar/volume load, are best introduced
after a reasonable fruit intake has been established. Because
fruit intake is reduced with such a diet, vitamin supplementation
might be necessary.
If tolerated, juices with equivalent fructose-glucose concentrations and low sorbitol concentrations or no sorbitol may be a good substitute for juices containing sorbitol and high concentrations of fructose along with low concentrations of glucose (see below).7 Juices, because of the relatively high sugar/volume load, are best introduced after a reasonable fruit intake has been established. Because fruit intake is reduced with such a diet, vitamin supplementation might be necessary.
D. More information
This type of fructose intolerance is not to be confused with hereditary fructose intolerance (dicussed below).
How is fructose (mal)absorbed?
It should be noted, however, that a study has shown that freshly pressed and unprocessed ("cloudy") apple juice did not influence stool frequency and consistency, compared with normal, enzymatically processed ("clear") apple juice, which significantly promoted diarrhoea. It was suggested that, in addition to fructose, the increased availability of non-absorbable monosaccharides and oligosaccharides as a result of the enzymatic processing of apple pulp is an important aetiological factor in apple juice-induced chronic non-specific diarrhoea (see below).10 It should be noted that not all countries use this method of processing fruit juice.
It can therefore be said that a combination of high fructose intake, a high ratio of fructose to glucose, and an individual's relative inability to absorb fructose all contribute to incomplete absorption and loose stools.1
Sorbitol is a sugar alcohol that also naturally occurs in fruits (and is added to other foods, but not to fruit juice, during commercial processing). Sorbitol is absorbed via passive diffusion at slow rates, resulting in much of the ingested sorbitol being unabsorbed. This is a further possible cause of loose stools, although the quantity of sorbitol in fruits is generally less than that of fructose. 1,6,11
It has also been shown that chilled fluids stimulate colonic propulsion and the urge to defecate. This may play a role in diarrhoea, as fruit juice is usually given chilled.4
Other GI symptoms may be
In infants, the main clinical feature of intolerance is the passage of watery stools with an acidic pH, often passed with flatus. Volume is variable and roughly proportional to the amount of malabsorbed carbohydrate that has been ingested.13 The intestinal transit in young infants is rapid in any case. Watery stools can thus be passed very frequently. Undigested or unabsorbed sugars, because of their osmotic effect, attract water into the intestine, where they are dissolved into a fluid that distends the gut wall. Increased peristalsis causes the passage of frequent fluid stools. This can quickly cause dehydration and metabolic acidosis. In older children and adults, the capacity to salvage carbohydrates from the large intestine is better developed. Adults with intolerance are thus more likely to complain of abdominal discomfort, borborygmi (rumblings) and flatulence and possibly less likely to have acute, watery diarrhoea.6
Non-GIT effects related
to fructose intolerance:
In isolated studies, fructose malabsorption has been associated with early signs of mental depression and low serum tryptophan concentration. Following a fructose- and sorbitol-reduced diet has been shown to improve mood and early signs of depression.15
It has been suggested that increases in crying and fussing duration may be an important clinical indicator of carbohydrate malabsorption in infants and that infant colic may be a important factor affecting carbohydrate malabsorption from fruit juices containing sorbitol and a high fructose-to-glucose ratio.16
Other dietary causes of
*Although high fat intake is sometimes implicated as a cause or aggravation of diarrhoea, low fat intake has also been implicated; the suspected mechanism being associated with fat's role in gastric emptying and alteration in intestinal motility (mouth-to-anus transit time).18
# For more information: www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?222700
What level of fructose is
In another study, fructose absorption was studied by the breath hydrogen test in 114 healthy children aged 0.1-6 years. These were given either 2 g/kg or 1 g/kg of fructose. All 57 children given 2 g/kg had peak breath hydrogen excretions > or = 20 ppm. At 1 g/kg, only 25/57 (44%) showed incomplete absorption. The percentage incompletely absorbing fructose and the peak breath hydrogen value were significantly higher in children aged 1-3 years. Interestingly, this age distribution correlates with that of toddlers' diarrhoea.22